Automatic fuel regulation of open hearth furnaces



Oct. 31, 1939. w. c HOGG ET AL AUTOMATIC FUEL REGULATION OF OPEN HEARTHFURNACES Filed Jlily 16, 1935 ATTORNEYS Patented Oct. 31, 1939 UNITEDSTATES PATENT OFFICE AUTOMATIC FUEL REGULATION OF OPE HEARTH FURNACESApplication July 16, 1935, Serial No. 31,736

2 Claims. (Cl. 23615) This invention relates'to open hearth furnaces andmore particularly to means to automatically regulate the fuel inputthereof to prevent buming of the refractory lining of the said furnace.

One of the objects of the presentinvention is to provide means toautomatically regulate the fuel input in response to temperatureconditions attained by the hottest point in the furnace. Another objectis to provide means responsive to temperature conditions attained in thefurnace to automatically regulate the fuel input to the furnace toprevent burning or melting of the refractory lining of the furnace.Other objects and advantages will appear as the invention is more fullydisclosed.

An open hearth furnace is fired alternately from one end to the other.We have found that the hottest point in the furnace is located at theneck or knuckles at either end of the furnace close to the rearskewback. When the furnace is being fired in one direction the outgoingneck is the hottest point. When the direction of firing is reversed theopposite neck becomes the hottest point.

In co-pending application Serial No. 31,735,

' filed July 16, 1935, by Lewis Rumford It, entitled Method and meansfor determining and automatically regulating furnace temperatures, thereis described and claimed a method and means for determining thetemperature of furnaces by measuring the radiant energy emitted by therefractory lining thereof. Lewis Rumford, II, one of the applicants ofthe present invention, is the same Lewis Rumford, II, applicant of theabove identified copending application.

In accordance with the invention of said copending application aradiation pyrometer device is sighted through an opening in a wall ofthe furnace upon the inner surface of another wall and a pressure of airor other suitable gas is blown through the opening into the interior ofthe furnace to prevent the escape of flame, dust and products ofcombustion through theopening which would interfere with the correctmeasurement of the radiant energy emitted by the inner wall surface.

When the furnace temperature is measured in the manner described in saidco-pending application we have found that the temperature of the roof islower than the temperature of the outgoing neck of the furnace. vConsequently while the roof may be prevented from deleteriousoverheating the outgoing neck cannot be so protected. By regulating thefuel input in response to tem perature conditions of the outgoing neck,however, the roof and other sections of the furnace thereby may beprotected from overheating.

Accordingly, the present invention contemplates an improvement in themethod of said copending application with respect to this feature andfurther with respect to fuel input regulation responsive to thetemperature conditions of the outgoing neck of the furnace. Referenceshould be made to the accompanying drawing wherein Fig. 1 is a plan viewof a typical open hearth furnace incorporating the present invention;

Fig. 2 is a cross-section along plane 22 of Fig. 1.

In the drawing the furnace is shown with back wall I, front wall 2 andneck side walls 3 and 4 respectively through which extend burners 5 and6 respectively. Walls 1 and 8 are the rear skewbacks as they are knownin the art. The hottest points in the furnace are points 9 and Ill;point 9 when burner 6 is operating and point I when burner is operating.Burners 5 and 6 are periodically operated to alternate the direction offiring.

In accordance with the present invention radiation pyrometer devices IIand I2 are sighted through appropriate openings l3 and H1 in the backwall 1 upon points 9 and 10 respectively. The electric energydeveloped-by said devices II and I2 is conducted by suitable electricconnections to double throw switch l5 electrically connected topyrometer controller mechanism Circuit arrangement A schematicallyillustrates a circuit diagram of a relay device to operate dou- -blethrow switch l5 to connect the pyrometer device II or l2 which issighted on the outgoing neck 9 or [0. Switch IT in circuit A may belocated in any convenient manner on the furnace reversing mechanism sothat upon reversing versible motor 24 opening and closing valve 25 inmain fuel supply conduit 26 therebyincreasing or decreasing the amountof fuel being supplied to burners 5 and 8. Hand operatedvalves 21 and 28control the direction of fuel feed to burners 5 and 6 and one of thesevalves is closed when the other is open. Switch I! (circuit A) may bearranged in mechanical combination with valves 27 and 28 to be operatedwith the reversing of burners 5 and 6. Such a mechanical combination ofan electrical switch with hand or motor operated valve heretofore hasbeen devised and specifically forms no part of the present invention anymore than do relay mechanisms l5 and 23 or reversible motor means 24.

In the practical application of the present invention contacts 2| and 22are adjusted so that when the temperature of the inner surface of theoutgoing neck of the furnace approximates F. below its danger or meltingpoint the relay switch 23 is thrown into circuit closing positionenergizing motor 24 to close off the fuel supply a certain maximum. Whenthe temperature of said inner surface drops below a determined minimumrelay switch 23 is again energized to close the other circuit toenergize the motor 24 in a reverse direction to open valve 25 permittingan increase in the furl supply to the furnace. These circuits areindicated by letters H and L respectively, letter C indicating thecentral or common ground circuit of the two.

In this manner the temperature of the furnace may be automaticallyregulated to be below a certain maximum determined by the temperatureattained by the outgoing neck which is the hottest point in the furnace,and also regulated to be at all times above a certain minimum. Therefractory lining of the entire furnace is thereby protected at alltimes from the deleterious effects of overheating.

Having broadly and specifically described the present invention it isapparent that many modifications and adaptations may be made thereinwithout departing essentially from the same, and all such modificationsand adaptations are contemplated as may fall within the scope of theaccompanying claims.

What we claim is:

1. Apparatus for regulating the temperature in a furnace of theregenerative type, provided with means to alternately supply heat energyat opposite ends thereof, said apparatus including a pair of radiationsensitive devices adapted to convert radiant heat energy into electricalenergy having an intensity bearing a known relation to the temperatureinducing said heat energy, means to irradiate each of said devices byradiation emitted by a portion of the inner refractory lining of saidfurnace which during each alternate heating, of the furnace is subjectedto the maximum heating eifects, means adapted to be actuated by theelectrical energy thereby produced in said devices to lower and toincrease the supply of heat energy to said furnace as the intensity ofsaid electrical energy approximates maximum and minimum limitsrespectively, and means to automatically connect to said heat supplycontrol means first one and then the other of said devices insynchronism with the alternate supplying of heat energy at opposite endsof the said furnace.

2. Means for regulating the temperature of a furnace heated fromopposite ends alternately at periodic intervals by the injection offluid fuel and oxidizing gases into the said furnace, said meanscomprising a pair of radiation sensitive devices adapted to convertradiant heat energy into electrical energy having an intensity bearing aknown relation to the temperature inducing said radiant heat energy,means to irradiate one of said devices wtih radiant heat energy emittedby a portion of the inner refractory surface of said furnace whichduring one period of heating of the furnace is subjected to the maximumheating effects, means to irradiate the other of said devices withradiant heat energy emitted by a portion of the inner refractory surfaceof the furnace which during the next succeeding period of heating issubjected to the maximum heating effects, means to supply fluid fuel tosaid furnace, means to direct the supply of fuel alternately to oppositeends of said furnace, means. to reduce the amount 1 of said fuel passingto said furnace a determined amount from a maximum, means to reversesaid reducing means, and means energized by the electrical currentgenerated in one of said devices during each heating period to actuatesaid reducing means and said reversing means when the intensity of saidelectrical energy approximates determined maximum and minimum limitsrespectively representative of temperature limits desired in saidfurnace.

WILLIAM C. HOGG. LEWIS RUMFORD, II.

